The invention relates to a rotary tube with an outer casing and at least one treatment tube in which can be arranged a heat supply, which is held in end plates and optionally in intermediate plates, these plates being supported in the outer casing.
During the thermal treatment of solids in indirectly heated rotary tubes, problems concerning the permissible stresses arise a treatment tube wall temperatures exceeding 450.degree. . Even with heat-resistant materials, the length of the rotary tube is restricted to a few metres, for example at temperatures of about 1000.degree. C, if no expensive intermediate bearings are provided.
With long treatment tubes which are to be heated, the problem arises of compensating for the thermal expansion relative to the colder outer casing which expands less. The same problem also arises with short treatment tubes which are heated to high temperatures. In both cases, the radial thermal expansion can give rise to problems.